GENUS MUSA. 



771 



STARCHES OF MUSACEit. 



Class, Monocotyledones. Order, Scitaminales. 

 Genus represented, Musa. 



GENUS MUSA. 



Family, Musaceae. 



The genus Musa, one of the four genera of Musaceoe, which includes about 50 species, comprises 

 about 20 species of tropical plants that are widely distributed, especially in the tropical regions of 

 the Old World. Some of the species or varieties are extensively cultivated, chiefly for the fruit 

 or for the fiber that is obtained from the tree-like stems, one species (M. textilis) being the source 

 of Manila hemp. Starches from 3 species were studied, including M. cavendishii Lamb. (M. 

 sinensis Sagot, M. chinensis Sweet), the Chinese dwarf banana, and known in the central parts of 

 America as the dwarf Jamaica banana; M. sapientum Linn., the conamon banana; and M. enseie 

 Gmel., the Abyssinian banana. The first is a native of Southern China, the second is a native of 

 India and the East Indian Islands, and the third a native of Abyssinia. There are at least a half 

 dozen varieties of M. sapientum, the most important being M. sapientum var. paradisiaca Hort. 

 {M. paradisiaca Linn.), which is commonly known as the plantain banana, cooking banana, or 

 Adam's fig; and most of the banana fruit of commerce in this country is of this variety. It is grown 

 extensively for its fruit, which is used as a food directly or in the form of " banana starch," the 

 latter being obtained from the unripe fruit. As the fruit ripens the starch disappears. M. caven- 

 dishii is extensively cultivated in the Southern States and West Indies, chiefly for its fruit. M. 

 ensete is the largest of the species, and is cultivated chiefly as a decorative plant. 



STARCH OF MUSA CAVENDISHII OBTAINED FROM THE STALK. 

 (Plate 79, figs. 469 and 470. Chart 320.) 



Histological Characteristics. — In form the grains are simple, and are isolated with the exception 

 of a few clumps. No pressure facets were observed. The surface of the grains is flattened and the 

 margin tends to be irregular, owing to depressions and rounded projections, and to nipple-like 

 processes. The edges of some grains are serrated and appear as though they had been eroded. The 

 conspicuous forms are the mussel-shell, clam-shell, and oyster-shell shapes. There are also ovoid, 

 circular, oval, elliptical, spindle, and various irregular 

 forms. The grains are very much flattened, and when 

 viewed from the end or edge are of a long, slender, and 

 more or less irregular spindle form. 



The hilum is a very small, round, non-refractive, not 

 very distinct spot, generally situated very eccentrically, 

 commonly at the base of a more or less distinct projec- 

 tion from the end, usually in the median line or only 

 slightly to one side. It is never fissured, and grains with 

 double hila were not seen. 



The lamellce are distinct and are in the form of fine rings 

 around the hilum and segments of rings beyond, which 

 follow the outline of the distal margin. Those at the 

 distal end are not so fine but more distinct than the others, 

 and they also vary in distinctness in different grains. In 

 fairly large grains the number is usually from 35 to 45. 



The grains vary in size from 8 to 80ft. The common 

 size is about 40ju. 



Polariscopic Properties. — The figure is usually very 

 eccentric, fairly distinct, but not clear-cut. Usually two 

 of its lines are visible which generally become very broad and dim toward the margin; the lines 

 may be bent or otherwise distorted, and often obscured in some part by variations in the degree of 

 polarization. The figure is distinct and clear-cut when the grain is viewed on edge or end. 



The degree of polarization is low. Polarization is often absent or very low in large areas of 

 the grain, which may be due in part at least to thinness of the substance at these points. Polariza- 

 tion is high when the grain is seen on edge or end and when overlapping of the grain occurs. 



P I GV T P 

 S 



Qart No. 320. 



GV S T CI CA PA FC F S CI PA CA 

 ^ ■ — ■ ' ' ■ ' PC PS 



Curve of Reaction- Intensities of Starch of Musa 

 cavendishii (stalk). 



